Compressor



p 9, 1941- o. LEPERSO NNE 2,255,359

' COMPRESSOR Filed June 21, 1938 2 Sheets-Sheet 1 Zwe/ 1' cicurezge/so/a/ae Patented Sept. 9, 1941 OFFICE COMPRESSOR Octave Lepersonne, Brussels, Belgium Application June 21, 1938, Serial No. 214,974 In France June 23, 1937 10 Claims.

The present invention relates to compressors for brakes and hydraulic transmissions of the compound type comprising two pistons of different diameters of which one, the low pressure piston, serves to, displace a comparatively large volume of liquid for a given travel and the other high pressure piston serves to displace a comparatively small volume of liquid and to create a high pressure. The back pressure in the low pressure cylinder is controlled by a member with spring return having a small surface subjected to the high pressure and a large surface subjected to the low pressure, and the ratio between these sections is less than the ratio of the sections of the high pressure and low pressure pistons in such manner as to graduallyreduce the said back pressure as the high pressure rises.

The invention has for its object a compressor of this type characterised by the low pressure cylinder communicating with a variable space, the variations in volume of which are controlled by a compensating piston operated by the actuating member which controls the back pressure in the high pressure cylinder, which obviates any possibility of inaccurate communication between the cylinders and the liquid reservoir and, owing to the action of the highpressure and low pressure on this compensating piston, permits of obviating any jerky transmission and of efiecting a perfect state of progress.

According to another characteristic, the compensating piston after having travelled over a distance such that the back pressure in the low pressure-cylinder has-fallen below a certain limit, is'subjected to an additional external pressure, for example that of a spring, causing a fresh back pressure in the low pressure cylinder and still'further improving the degree of progress of the transmission.

According to another characteristic, the compensating piston co-operates with a stop restricting its displacement so as to produce at the end of the clamping stroke serving in case of extreme braking, a considerable increase in the back pressure and to thus limit the high pressure developed by the compressor whatever may be the effort applied at this moment to the piston.

According to another characteristic also, the variable section piston may move by an amount determined with respect to the thrust under the action of a return spring bearing on this thrust and the tension of which is greater than that of the spring bringing the graduated piston back to the rear, this displacement having as a result to block the port placing the low pressure cylinder in communication with the reservoir and to keep at rest a positiveresidual pressure in the interior of the pipes and receivers.

Other characteristics will appear in the course of the following description.

In the accompanying drawings, by way of example:

Figure 1 is a longitudinal section on the axis of the compressor according to the invention,

Figure 2 is a partial section similar to that of Figure 1 and illustrating another method of carrying out the invention,

.Figures 3 and 4 indicate diagrammatically two different phases of the movement of the parts.

According to the construction shown in Figure 1, the compressor according to theinvention is composed of a body I comprising two co-axial sections having bores 2 and the smaller one 3 of which is screwed at 4 in the interior of the larger one. A packing 5 prevents leakage between the sections and the smaller section is terminated by a socket 6 for connection to piping and thus to receivers. This body I also comprises a socket l which may be connected to a reservoir containing the liquid and which may be placed in communication by an aperture 8 with the bore 2.

In the interior of the two bores 2 and 3, slides a stepped piston 9, ill, the portion ID of which of smaller diameter or the high pressure piston slides in the interior of the bore 3 of high pressure cylinder and is pi'ovided with a tight packing ring l2 and the part 9 of which of greater diameter or the low pressure piston slides in the interior of the bore 2 or low pressure cylinder and is providedwith a packing II closing the aperture 8 when the piston is at rest. The stepped piston 9, I 0 is urged towards the rear by a spring l3 bearing on the bottom of the low pressure cylinder 2, and it is driven forward by a block I4 on which is screwed at l5 a sleeve l5 sliding in the bore 2, provided with a packing joint H. The movement of the sleeve towards the rear is limited by a series of stops I8 fixed to the body' I. The sleeve l6 comprises an extension l9 adapted to come into contact by its circular flange 20 with a rear extension 2| of the low pressure piston 9 and adapted to slide in the 'interior of a bore 22 made in the rear portion of the low pressure piston 9, the relative movement of the sleeve I6 with respect to the low pressure piston 9 being limited by a stop 23 fixed to this socket l6 and moving in a recess 24 made in the rear extension .2l of the low pressure piston 9. The stop 23 acts upon forced in the direction of the lower part of the socket 56 by a spring the rear of the recess 24 to hold the pistons 9 and 19 in their respective positions under the influence of spring 32 when the device is at rest.

In the interior of the stepped piston 9, I is produced a coaxial bore 25 in which a piston 26 called compensating piston is adapted to slide, the head 21 of the piston 26 being provided with a packing ring 28 moves in the bore 22 made at the rear of the low pressure piston 9. This bore 22 communicates by apertures 29 with an annular chamber 36 surrounding the rear extension 2! of the low pressure piston 9, which may itself be connected to the socket 1 and the liquid reservoir by the port 3| made in the body I. The compensating piston 26 is constantly the receiving devices to its idle position by a spring 32 bearing on the block l4 and of which the tension is greater than that of the spring l3, and the piston 26 is provided with a cavity 33 into which penetrates an extension 34 of the driver 14 around which is arranged a spring 35, bearing on the block l4 and adapted when the compensating piston'26 recedes, to contact with the edges of the cavity 33.

At the extremity on the high pressure side of the compensating piston 26, there is screwed at 36 a hollow rod 31 constituting the .control member. This hollow rod 31 slides in a bore 38 made in the high pressure piston In, it is closed at it's extremity 39 and it is provided with ports 40 uncovered when the piston 26 is at the end of its stroke, but adapted to be closed when the.

piston 26 recedes with respect to the high pressure piston [0, either by the surfaces of the bore of the high pressure piston or by an annular packing piece 4! fixed in a groove 32 made at the extremity of the high pressure piston 16 and independent of the packing l2 of this piston H]. The hollow rod 31 communicates with the low pressure cylinder 2 by the conduits 43, the conduits 44 and 45 made in the piston 26 and the conduits .46 made in the surfaces or the bore 25.

If s and S are the respective sections of the high pressure and low pressure pistons and s1 and S1 are the respective sections of the rod 31 subjected to the action of the high pressure and the reference 26 designates the body of the compensating piston subjected to the action of the low pressure, these different sections are such that the ratio is less than the ratio Finally, the low pressure cylinder is provided with a socket 50' connected by the conduit to the socket 1. In this-socket 56, closed by the threaded plug 52, is a valve 53 with spring 54 adapted to place the socket 56 in communication with the low pressure cylinder 2 through the conduit 55. The seat 56 of the valve 53 forms a poppet valve and is appliedstrongly against 51 bearing on the bottom of the threaded plug 52, which permits by unscrewing this plug 52 of diminishing or removing the tension of the said spring 51.

This compressor operates in four phases: In the course of the first phase the block I4 is acted upon in the direction of arrow 1, the flange 20 of the socket l6 comes into contact with the rear extension 2i of the stepped piston 9, i6 and the assembly of the block l4, socket i6, stepped piston 9, l0 and compensator piston 26 thrust by the spring 32, moves in the direction of the arrow f. The port 8 placing the low pressure cylinder in communication with the reservoir is blocked, whilst the ports 46 are open, placing the low pressure cylinder through the conduits 46, 45, 44 and 43 in communication with the high pressure cylinder. The liquid compressed by the high pressure piston is forced directly towards the receiver and the liquid acted upon by the low pressure piston and the compensator piston 26 is forced towards the high pressure cylinder through the port 40. It is thus seen that the three pistons: high pressure In, low pressure 9, and compensating piston 26, concur in driving the liquid towards the receiver. The high pressure and low pressure increase simultaneously.

In the course of the second phase. when the compensating piston 26 recedes, compressing the spring 32, this receding movement creates a cavity at the front of the compensating piston, in which cavity the liquid compressed in the chamber 2 of the low pressure cylinder penetrates; it is therefore apparent that the pressure falls in the low pressure cylinder, the liquid contained in the chamber 22 at the back ,of the compensating piston 26 returning to the reservoir through the openings 29, the annular chamber 30 and the port 3|.

The liquid in the cavity 22 locatedbehind the piston 21 is thus driven towards the reservoir and the backward movement of the compensating piston 26 also efiects the blocking of the port 40 by the packing 4!. It is thus seen that at this moment only the high pressure piston serves. to send liquid towards the receivers the low pressure piston and the compensating piston 26 being shut off from these receivers. The back pressure acting on the low pressure piston diminishes, whilst the high pressure acting on the rod 31 of the compensating piston 26 increases. After a definite travel of the compensating piston 26 and when the back pressure on the low pressure piston'has fallen below a certain value, for example being cancelled, the compensating piston 26 comes into contact with the spring 35.

In the course of this third phase, the compensating piston 26 contacts with the spring 35, a fresh back pressure acting on the low pressure piston appears, which back pressure increases accordingly as the springs 32 and 35 are compressed and modifies the ratio'between the increase of the motive pressure and that of the efiort applied on the stepped piston.

Finally, in the course of the fourth phase, the extension 34 of the block 14 which has penetrated into the cavity 33 of the piston 26 comes into contact with the bottom of this cavity 33 forming a stop for the piston 26, the return movement of which stops. At this moment, the ports 40 and the port 8 being blocked and cavity located at the rear of the low pressure piston 9 and between this low the compensator piston 26 being a closed cavity, the low pressure piston 9 abuts against the liquid contained in the low pressure cylinder 2 which constitutes a closed space, the movement of the stepped piston 9, 16 stops. Any further force applied to block l4 cannot move the pistons 9, l0, and [2 because of the trapped pressure piston and.

fluid ahead of piston 9-H in chambers 2-45 and, as a result, the pressure in the brake cyL- inders constituting the receivers cannot be increased and remains constant after means 34 and 33 engage. It is seen that the stop of the piston 26 on the extension 34- of the block H permits of limiting the maximum pressure communicated to the liquid whatever may be the effort exerted on the stepped piston 9, II).

On the return and as soon as the effort exerted on the block I4 is suppressed, the stepped piston 9, I is brought to its position of rest under the combined action of the spring l3 and of the pressure of the liquid delivered by the receivers, the compensating piston 26 also returns to its position of rest by the action of springs 32 and 33, the liquid penetrates afresh through the port 3|, the annular chamber 30 and the orifices 29 into the cavity 22, and the ports 40 are uncovered afresh, placing in communication the receivers, the conduits, the high pressure cylinder, the low pressure cylinder and the reservoir through the port 8 which is then uncovered. Under the action of the depression created in the low pressure cylinder by the sudden return backward of the low pressure piston, the valve 53 opens and the liquid from the reservoir penetrates into the low pressure cylinder through the orifice 55, thus filling up the depression in this cylinder.

The valve 53 may be omitted and the fresh supply with liquid of the low pressure cylinder may be effected by the deflection of the packing piece of the low pressure piston which is produced when a partial vacuum is created in this cylinder, which forces the liquid which is behind the piston in the chamber 30 to pass into this cylinder. .This described structure is not illustrated in the present drawings but is designed to disclose an alternative construction which may replace the valve construction corresponding to member 53.

As long as the pressure of the liquid delivered by the receivers is sufficient, the stepped piston 9, i0 compresses the spring 32 and the port 8 remains uncovered, permitting the liquid to return to the reservoir. But as soon as the pressure in the cylinders falls below a certain definite limit fixed by the difierence of tension of the springs 32 and I3, the spring 32 having a tension greater than that of-the spring {3 becomes preponderant, the stepped piston 9, l0 moves afresh in the direction of the arrow 1 by an amount equal to or less than the play of the stop 23 in the interior of the recess 24 and until the port 8 is blocked afresh, which permits'of maintaining in the conduits and receivers, a definite positive residual pressure.

If in consequence of heating when at rest, the liquid contained in the piping and receivers expands, it again compresses the spring 32, the port 8 is uncovered and the liquid escapes towards the reservoir until the residual pressure has fallen to the value chosen. If, on the contrary, the liquid tends to contract, the spring 32 causes the stepped piston 9, I 0 to advance slightly until the residual pressure attains the selected value.

As has already been pointed out, if in the course of-working, a depression appears in the low pressure cylinder, the valve 53 opens and permits the liquid from the reservoir to penetrate into the low pressure cylinder and to fill up this depression.

Finally, in the course of filling up the compressor, the threaded plug 52 is unscrewed in such manner as to diminish or destroy the tension of the spring 51 and the air compressed by the low pressure piston causes the lifting of the seat 56 forming a poppet valve and thus escapes towards the reservoir.

It appears from this description that the compressor according to the invention permits of effecting the approach of the brake segments with a reduced movement of the motive pistons and it also permits of the progressive passage from the phase of low pressure to the phase pressure piston.

It should also be noted that to realise one or more supplementary degrees in the proportion between the braking effort and the motive effort, there could be arranged one or more springs similar to the spring 35 set back with respect thereto and each with respect to the others.

' It must finally be pointed out that the device utilised to maintain the residual pressure permits when at rest of keeping filled with liquid under pressure not only the pipes and receivers but also the cylinders of the compressor owing to the communication efiected by the opening when at rest of the ports 40 so as to overcome the passive resistances of the movable system in the cylinders, and of ensuring an immediate start.

In Figure 2 is shown a modification of the compressor according to the invention. In this embodiment, the communication between the low pressure cylinder and the high pressure cylinder is effected by means of the port 60 made in the wall of the high pressure cylinder uncovered when at rest and which is blocked by the packing piece I2 as soon as the stepped piston 9, I 0 commences its movement in the direction of the arrow f and by means of a valve 6| subjected to the action of the draw-back spring 62 and opening only in the direction placing the low pressure cylinder in communication'with the high pressure cylinder by means of the hollow rod 31 which no longer comprises ports 40 but is open at its extremity, the packing 4| having simply for its object to ensure a tight joint between this hollow rod 31 and the place-where it' is held in the extremity of the high pressure piston.

The operation in the case of the construction according to Figure 2 is similar to the preceding one but with the following differences:

In the course of the second phase, the low pressure piston instead of being cut oil from the receivers at the same time as the compensating piston 25, only ceases to send liquid towards these receivers when the pressure in the low pressure cylinder has become sufliciently less than the pressure in the high pressure cylinder, to cause the closing of the valve GI and consequently the placing out of operation of the low pressure piston with respect to the receivers.

The method of creating and maintaining the I age is avoided.

The invention is not restricted to the exact constructions shown and described which are only given by way of example,

What I claim is:

1. A compressor for fluid pressure, comprising a high pressure cylinder, having means for communication with a receiving device, a high pres sure piston operable in said cylinder, a low pressure cylinder coaxial with the high pressure cylinder, a low pressure piston operating in the low pressure cylinder, the pistons being arranged integrally, said pistons having a compensating cylinder of smaller diameter extending within the low pressure piston, a compensating piston operative in the compensating cylinder, the end of the extension of the compensating piston terminating in the high pressure cylinder, springs acting on the compensating piston, means for simultaneously displacing the three pistons in their cylinders, said first piston having openings for establishing communication between the low pressure cylinder and the compensating cylinder and other openings for establishing communication between the compensating cylinder and the high pressure cylinder, means for closing these last named openings when the pressure in the high pressure cylinder reaches a predetermined value, a chamber of variable volume created by the displacement of the compensating piston and arranged at the rear of said piston, and having a communication between this chamber and the low pressure cylinder, and means for gradually increasing the volume of this chamber by the displacement of the compensating piston when the pressure in the high pressure cylinder exceeds said predetermined value.

2. A compressor for fluid pressure, comprising a high pressure cylinder, having means for communicating with a receiving device, a piston operative in the high pressure cylinder, a low pressure cylinder coaxially disposed with respect to'the high pressure cylinder, a piston in the low pressure cylinder, and integral with the first piston, said piston being coaxial, said second piston being bored to provide a compensating cylinder of smaller diameter, a compensating piston operative in the compensating cylinder, springs acting on the compensating piston, one end of the eX- tension of the compensating piston terminating in the high pressure cylinder, means for simultaneously disp aci g the three pistons in their cylinders, said first piston leaving openings between the low pressure cylinder and the compensating cylinder and other openings afiording communication between the compensating cylinder and the high pressurecylinder, means for closing these last named openings when the pressure in the high pressure cylinder reaches a predetermined value, said compressor having a chamber of variable volume created by the displacement of the compensating piston and arranged at the rear of said piston, and having communication between said chamber and the low pressure cylinder, means for increasing the volume of said chamber by the displacement of the compensating piston simultaneouslyv with the increase of pressure in the high pressure cylinder, and resilient means of predetermined tension acting on the compensating piston to reduce the volume of said chamber.

3. A compressor for fluid pressure, comprising a high pressure cylinder, having means for connection with a receiving, device, a piston operative in the high pressure cylinder, a low pressure cylinder, a piston operative in the low pressure cylinder, and integral with the first piston, the respective pistons and cylinders being coaxial, said second piston having a bore constituting a compensating cylinder, a compensating piston operative therein, springs acting on the compensating piston, the compensating piston terminating in the high pressure cylinder, means for simultaneously displacing the three pistons in their cylinders, said first piston having openings for the communication between the low pressure cylinder and the compensating cylinder and other openings for communication between the compensating cylinder and the high pressure cylinder, means for closing these last named openings when the pressure in the high pressure cylinder reaches a predetermined value, said compressor having a chamber of variable volume created by the displacement of the compensating piston, said chamber being arranged at the rear of said compensating piston, said compressor having communication between said chamber and the high pressure cylinder, means for closing the communication when the pressure in the high pressure cylinder reaches a predetermined value, the compensating piston having separated surfaces subjected respectively and simultaneously to the pressure in the low pressure cylinder, and resilient means acting on said surfaces, the annular surface of the compensating piston subjected to the low pressure being greater than the surface of the extension of said compensating piston subjected to the high pressure.

4. A compressor for fluid pressure, comprising a high pressure cylinder having means aifording communication from this cylinder to receiving devices, a piston operative in said high pressure cylinder, at low pressure cylinder, a piston operative in said low pressure cylinder, and integral with the first piston, said cylinders and pistons being coaxial, said second cylinder having a bore constituting a compensating cylinder of relatively smaller diameter, a compensating piston operative in the compensating cylinder, springs acting on the compensating piston, said compensating cylinder leaving an end terminating in the high pressure cylinder, means for simultaneously displacing the three pistons in their cylinders, said first piston having openings for communication between the low pressure cylinder and the compensating cylinder and other openings for communication between the compensating cylinder .and the high pressure cylinder, means for closing these last named openings when the pressure in the high pressure cylinder reaches a predetermined value, a chamber of variable volume created by the displacement of the compensating piston and arranged at the rear of said piston, said compressor having communication between this chamber and the high pressure cylinder, means for closing such communication when the pressure in the high pressure cylinder reaches a predetermined value, the compensating piston having an annular surface subjected to the pressure in the low pressure cylinder and simultaneously an extension subjected to the pressure in the high pressure cylinder, the ratio between the annular surface of the compensating piston and the surface of its extension subjected to the respective pressures being greater than the ratio between the annular surface of the low pressure piston and that of the high pressure piston subjected to the same respective pressures.

5. A compressor for fluid pressures, comprising a high pressure cylinder, having means for communicating the high pressure cylinder to the receiving devices, a piston operative in the cylinder,-

a low pressure cylinder, a piston operative in the low pressure cylinder, and integral with the first piston the respective pistons and cylinders being arranged coaxially, said first piston having a bore forming a compensating cylinder of relatively small diameter, a compensating piston operative in the compensating cylinder, springs acting on the compensating piston, the end of the extension of the compensating piston terminating in the high pressure cylinder, means for simultaneously displacing the three pistons in their cylinders, said first piston having communicating openings between the low pressure cylinder and the compensating cylinder and other communicating openings between the compensating cylinder and the high pressure cylinder, means for closing these last named openings when the pressure in the high pressure cylinder reaches a predetermined value, said means being controlled by the relative displacement of the compensating piston and of the low and high pressure pistons in order to close the communication between the high and low pressure cylinders.

6. A compressor for fluid pressures, comprising a high pressure cylinder having means for communicating the high pressure cylinder to the receiving devices, a piston operative in the high pressure cylinder, a low pressure cylinder, a piston in the low pressure cylinder, integral with the first piston, the pistons and cylinders being arranged coaxially, said first piston having a bore forming a compensating cylinder, a compensating piston adapted to operate in said cylinder, springs acting on said compensating piston, the end of the extension of the compensating piston terminating in the high pressure cylinder, means for simultaneously displacing the three pistons in theircylinders, said first piston having openings forcommunication between the low pressure cylinder and the compensating cylinder and other openings for communication between the compensating cylinder and the high pressure cylinder, means for closing these last named openings when the pressure in the high pressure cylinder reaches a predetermined value, said compressor having a chambenof variable volume created by the displacement of the compensating piston and arranged at the rear of said piston, saidcompressor having cominunication between this chamber and the high pressure cylinder, means for closing this communication when the pressure in the high pressure cylinder reaches a predetermined value, the compensating piston being formed with separated surfaces subjected piston being formed with separated surfaces subjected respectively and simultaneously to the pressure in the low pressure cylinder and the pressure in the high pressure cylinder, resilient means acting on the and integral with the first piston the pistons and cylinders being coaxial, said first piston having a bore constituting a compensating cylinder,

a compensating piston operative therein, springs acting on said compensating piston, the end of the compensating piston terminating in the high pressure cylinder, means for simultaneously displacing the three pistons in their cylinders, said first piston having openings establishing communication between the low pressure cylinder and compensating cylinder and other openings establishing communication between the com- ,pensating cylinder and the high pressure cylinder, means for closing the last named openings when the pressure in the high pressure cylinder reaches a predetermined value, said compressor having a chamber of variable volume created by the displacement of the compensating piston and arranged at the rear of said piston, said compressor having communication between said 4 chamber and the low pressure cylinder, means compensating piston in a direction opposite to for gradually increasing the volume of the chamher when the pressure in the high pressure cylinder exceeds the said predetermined value, said compressor having means for admitting liquid from a reservoir to-thelow pressure cylinder, and means for closing the latter after a small displacement of the low pressure piston in its cylinder, when the compressor is at rest.

8. A compressor for fluid pressures, comprising a high pressure cylinder arranged for communication with receiving devices, a piston operative in the high pressure cylinder, a low pressure cylinder, a piston in the low pressure cylinder, the pistons and cylinders being arranged integrally and having a bore forming a compensating cylinder, a compensating piston adapted to operate in said compensating cylinder, springs acting on said compensating piston, an extension on the compensating piston terminating in the high pressure cylinder, means for simultaneously displacing the three pistons in their cylinders, said first cylinder having openings for communication between the low pressure cylinder and the compensating cylinder and other openings for communication between the compensating cylinder and the high pressure cylinder, means for closing these last named openings when the pressure in the high pressure cylinder reaches a predetermined value, said compressor having a chamber of variable volume under displacement of the compensating piston and arranged at the rear of said piston, said compressor having communication between this chamber and the high pressure cylinder, means for closing this last communicationwhen the pressure in the high pressure cylinder reaches a predetermined value, the compensating piston being formed with separated surfaces subjected respectively and simultaneously to the pressure in the low pressure cylinder and the pressure in the high pressure cylinder, resilient means acting on the compensating piston in a direction opposite to the pressures acting on the separated surface thereof, this resilient means comprising several springs adapted to successively abut the compensating piston, and means for modifying the initial tension of these springs.

9. A construction according to claim 1,, including a means for a communication between a liquid reservoir and the low pressure cylinder, a valve in said last means opening in a direction from the reservoir toward the low pressure cylinder, said valve having a seat capable of opening in the opposite direction under the action of the pressure in the low pressure cylinder, and a spring resisting movement of the valve seat. 7

10. A compressor for fluid pressure, comprising a high pressure cylinder adapted for communication with receiving devices, a high pressure piston operable in said cylinder, 2. low pressure cylinder coaxial with the high pressure cylinder, 2. low pressure piston operating in the low pressure cylinder, the pistons being integral, said pistons having a compensating cylinder of smaller diameter, a hollow compensating piston operative in the compensating cylinder and extending within the low pressure piston, springs acting on the compensating piston, the compensating piston having an extension terminating in the high pressure cylinder, means for simultaneously displacing the three pistons in their cylinders, said pistons having openings for establishing communication between the low pressure cylinder and the compensating cylinder and other openings for establishing communication between the compensating cylinder and the high pressure cylinder, means for closing these last named openings when the pressure in the high pressure cylinder reaches a predetermined value, said means comprising a valve opening from the low pressure cylinder toward the high pressure cylinder against the resilient means of a spring, said valve being positioned internally of the extension of the compensating'piston terminating in the high pressure cylinder.

OCTAVE LEPERSONNE. 

